EXCLUSIVE: The site, which claims to have obtained transfer documents relating to Gareth Bale and Anthony Martial, is accused of sending threatening emails demanding the money in return for their silence

But MirrorFootball can today reveal that Football Leaks, who claim to be “fighting for transparency in the world of football”, is accused of trying to extort millions of euros in exchange for not releasing more contract information.

Emails which appear to have come from people behind the Football Leaks site seen by this newspaper tell a story of information gathered in suspect circumstances and used to try and blackmail Doyen Sports, a leading agency and the one most affected by these leaks, into silence in exchange for up to €1million.

The man responsible for the blackmail, who goes under the (presumably false) name Artem Lovuzov, promises to stay silent during negotiations over his attempted extortion - coinciding with a fallow period of leaks on the site - before resuming the tide of revelations.

Revealed: Football Leaks claimed to have details of Gareth Bale's move to Real Madrid

The man, writing from an email address apparently registered in Kazakhstan, tells Doyen CEO Nelio Lucas over emails that were sent in October: “The leak is a lot bigger than you imagine…” but adds: “A generous donation, and you can be sure that all the information I possess will be destroyed.”

When asked what is meant by “generous”, Lovuzov replies: “I think something between €500,000 and a million would be a good donation for this material, but I want to see your suggestion.”

When he doesn't hear back, Lovuzov sends another threat.

“Two days have passed already and my lawyer tells me that he has not been contacted by you or your lawyer,” it read.

“As I told you, I am a man of my word, and as well as stopping all publications I decided to delete all the documents from the site to prevent any kind of speculation.

“For that reason, I'm giving you until 16.00 on Tuesday (continental Portuguese time) to contact my lawyer with a view to a proper resolution to this impasse. If not, the links will be reactivated and the new publications will appear. As well as that, from that moment on, I will initiate serious conversations with those newspapers.

“I await updates.”

Football Leaks did not exist until September 2015, but made its first big splash in Holland where it exposed a third-party agreement between FC Twente and Doyen where the Eredivisie side had sold rights to a number of players, including now-Southampton winger Dusan Tadic.

Dusan Tadic: The former FC Twente star's contract was also revealed by Football Leaks (Image: Ian Walton/Getty)

Twente’s arrangement is being investigated by the Dutch FA to see if it contravened their rules, but the revelations have prompted the resignation of Twente chairman Aldo van der Laan.

Those behind the site are thought to be Portuguese, but are now using Russian servers after two previous incarnations of the site were shut down for legal reasons.

The head of FIFA's transfer matching system, Mark Goddard, publicly referenced Football Leaks this week.

"It would be really good if we could have a verifiable, transparent, credible source as opposed to just back pages, and soccer leaks websites," he said.

"In the end the market funds out this information but they do it in a very unofficial, unstructured way and that really allows a lot of the opacity and the wheeling and dealing to be done. That's a real shame.

"For us, all streams of information are very, very useful and that one has been as well, we have a number of resources and places that we go to and that's become another one."

The authorities in Portugal are investigating the attempted extortion, as well as attempting to ascertain how Football Leaks procured the documents that have been published.